WO2023048515A1

WO2023048515A1 - Method and device for transmitting and receiving rapid data in communication system

Info

Publication number: WO2023048515A1
Application number: PCT/KR2022/014292
Authority: WO
Inventors: 김용호
Original assignee: 현대자동차주식회사; 기아 주식회사; 한국교통대학교산학협력단
Priority date: 2021-09-24
Filing date: 2022-09-23
Publication date: 2023-03-30
Also published as: KR20230043759A; US20240237070A1; CN118020375A; EP4408110A1

Abstract

Disclosed are a method and device for transmitting and receiving rapid data in a communication system. An AP method comprises the steps of: setting a first TS for a first STA; setting a second TS for a second STA; transmitting a first data frame of the first STA in the first TS; and transmitting a second data frame of the second STA in a transmission interval including the second TS, wherein the first TS and the second TS are sequentially set in an rTWT SP.

Description

Method and apparatus for transmitting and receiving rapid data in a communication system

The present invention relates to a wireless local area network (WLAN) communication technology, and more particularly, to a technology for rapidly transmitting time-sensitive data.

Recently, as the spread of mobile devices expands, a wireless local area network (WLAN) technology capable of providing fast wireless communication services to mobile devices is receiving much attention. The wireless LAN technology may be a technology that allows mobile devices such as smart phones, smart pads, laptop computers, portable multimedia players, and embedded devices to wirelessly access the Internet based on wireless communication technology in a short distance.

As applications requiring higher throughput and applications requiring real-time transmission occur, the IEEE 802.11be standard, which is an Extreme High Throughput (EHT) wireless LAN technology, is being developed. A goal of the IEEE 802.11be standard may be to support throughput rates as high as 30 Gbps. The IEEE 802.11be standard may support a technique for reducing transmission delay. In addition, the IEEE 802.11be standard includes a more expanded frequency bandwidth (eg, 320 MHz bandwidth), multi-link transmission and aggregation operation including operation using multi-band, A multiple access point (AP) transmission operation and/or an efficient retransmission operation (eg, a hybrid automatic repeat request (HARQ) operation) may be supported.

For low-latency operation in a WLAN, improvement of a conventional CSMA (Carrier Sensing Multiple Access/Collision Avoidance) scheme may be required. To transmit data based on the CAMA method, a communication node can check whether a channel is idle by performing a channel access procedure. When the channel is idle, the communication node can transmit data. That is, communication nodes can compete with other communication nodes to transmit data. Since it takes time due to contention, there may be a limit to quickly transmitting data.

On the other hand, the background technology of the invention is prepared to enhance understanding of the background of the invention, and may include content other than the prior art already known to those skilled in the art to which the technology belongs.

An object of the present invention to solve the above problems is to provide a method and apparatus for rapidly transmitting and receiving time-sensitive data in a communication system.

To achieve the above object, a method of an AP according to a first embodiment of the present invention includes setting a first TS for a first STA, setting a second TS for a second STA, and the first STA Transmitting a first data frame of in the first TS, and transmitting a second data frame of the second STA in a transmission period including the second TS, wherein the first TS and the first 2 TS are sequentially set within the rTWT SP.

Setting the first TS for the first STA includes receiving a TWT setup request frame from the first STA, and transmitting a TWT setup response frame to the first STA in response to the TWT setup request frame At least one of the TWT setup request frame and the TWT setup response frame may include offset information and duration information of the first TS, the offset information from the start time of the rTWT SP An offset up to the start of the first TS may be indicated.

Among the nominal minimum TWT wake duration included in the TWT setup request frame or the TWT setup response frame, x bits may indicate the offset information, and among the nominal minimum TWT wake duration, y bits may indicate the duration information. , and each of x and y may be a natural number.

Each of the first data frame and the second data frame may be transmitted after a successful channel access procedure.

The transmission procedure of the second data frame may be initiated after "the first data frame + SIFS + reception response frame + SIFS".

Padding may be added to the first data frame so that the transmission procedure of the second data frame is started after the start of the second TS.

The header of the first data frame may include information indicative of adding padding to a reception response frame for the first data frame.

A method of an STA according to a second embodiment of the present invention for achieving the above object includes transmitting a TWT setup request frame to an AP, and receiving a TWT setup response frame from the AP in response to the TWT setup request frame and receiving a data frame from the AP within a time slot (TS) established by the exchange of the TWT setup request frame and the TWT setup response frame, wherein the TS is established within an rTWT SP.

At least one of the TWT setup request frame and the TWT setup response frame may include offset information and duration information of the TS, and the offset information indicates an offset from the start time of the rTWT SP to the start time of the TS can do.

The method of the STA may further include transmitting a reception response frame for the data frame to the AP, wherein a header of the data frame indicates adding padding to the reception response frame for the data frame In the case of including the information to, the padding may be added to the reception response frame.

An AP according to a third embodiment of the present invention for achieving the above object includes a processor and a memory storing one or more instructions executed by the processor, wherein the one or more instructions include a first command for a first STA. Setting a TS, configuring a second TS for a second STA, transmitting a first data frame of the first STA in the first TS, and transmitting a second data frame of the second STA to the second TS , and the first TS and the second TS may be sequentially set within the rTWT SP.

When configuring the first TS for the first STA, the one or more commands receive a TWT setup request frame from the first STA, and a TWT setup response frame in response to the TWT setup request frame. It may be further executed to be transmitted to 1 STA, and at least one of the TWT setup request frame or the TWT setup response frame may include offset information and duration information of the 1st TS, wherein the offset information is the start of the rTWT SP An offset from the start point of the first TS may be indicated.

According to the present application, a plurality of transmission intervals can be set, and the first communication node can quickly transmit data (eg, time-sensitive data) in each of the plurality of transmission intervals. The second communication node may receive data in a transmission interval for itself among a plurality of transmission intervals. That is, since data can be transmitted and received at a preset time, data transmission delay may not occur. Therefore, the performance of the communication system can be improved.

1 is a block diagram showing a first embodiment of a communication node constituting a wireless LAN system.

2 is a conceptual diagram illustrating a first embodiment of multiple links established between MLDs.

3 is a timing diagram illustrating a first embodiment of a slot allocation method for a slot-based limited TWT.

4 is a conceptual diagram illustrating a first embodiment of a frame format for negotiating parameters of a slot-based restricted TWT.

5 is a timing diagram illustrating a first embodiment of a communication method according to slot-based limited TWT.

6 is a timing diagram illustrating a second embodiment of a communication method according to slot-based limited TWT.

7A is a timing diagram illustrating a third embodiment of a communication method according to slot-based limited TWT.

7B is a timing diagram illustrating a fourth embodiment of a communication method according to slot-based limited TWT.

7C is a timing diagram illustrating a fifth embodiment of a communication method according to slot-based limited TWT.

8 is a timing diagram illustrating a sixth embodiment of a communication method according to slot-based limited TWT.

9A is a timing diagram illustrating a seventh embodiment of a communication method according to slot-based limited TWT.

9B is a timing diagram illustrating an eighth embodiment of a communication method according to slot-based limited TWT.

10 is a timing diagram illustrating a ninth embodiment of a communication method according to slot-based limited TWT.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The term "and/or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

In embodiments of the present application, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B”. Also, in the embodiments of the present application, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B”.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

In the following, a wireless communication system to which embodiments according to the present invention are applied will be described. A wireless communication system to which embodiments according to the present invention are applied is not limited to the content described below, and embodiments according to the present invention can be applied to various wireless communication systems. A wireless communication system may be referred to as a “wireless communication network”.

In an embodiment, “setting an operation (eg, transmission operation)” means “setting information for the corresponding operation (eg, information element, parameter)” and/or “performing the corresponding operation”. It may mean that the "instructing information" is signaled. "Setting an information element (eg, parameter)" may mean that a corresponding information element is signaled. "Configuring a resource (eg, a resource region)" may mean that configuration information of a corresponding resource is signaled.

Referring to FIG. 1 , a communication node 100 may be an access point, a station, an access point (AP) multi-link device (MLD), or a non-AP MLD. An access point may mean an AP, and a station may mean an STA or a non-AP STA. An operating channel width supported by the access point may be 20 MHz (megahertz), 80 MHz, 160 MHz, or the like. The operating channel width supported by the station may be 20 MHz, 80 MHz, etc.

The communication node 100 may include at least one processor 110, a memory 120, and at least one transceiver 130 connected to a network to perform communication. The transceiver 130 may be referred to as a transceiver, a radio frequency (RF) unit, or an RF module. In addition, the communication node 100 may further include an input interface device 140, an output interface device 150, a storage device 160, and the like. Each component included in the communication node 100 may be connected by a bus 170 to communicate with each other.

However, each component included in the communication node 100 may be connected through an individual interface or an individual bus centered on the processor 110 instead of the common bus 170 . For example, the processor 110 may be connected to at least one of the memory 120, the transceiver 130, the input interface device 140, the output interface device 150, and the storage device 160 through a dedicated interface. .

The processor 110 may execute a program command stored in at least one of the memory 120 and the storage device 160 . The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 120 and the storage device 160 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 120 may include at least one of a read only memory (ROM) and a random access memory (RAM).

2 is a conceptual diagram illustrating a first embodiment of multi-link established between multi-link devices (MLDs).

Referring to FIG. 2, an MLD may have one medium access control (MAC) address. In embodiments, MLD may refer to AP MLD and/or non-AP MLD. The MAC address of the MLD may be used in a multi-link setup procedure between a non-AP MLD and an AP MLD. The AP MLD's MAC address may be different from the non-AP MLD's MAC address. Access point(s) associated with the AP MLD may have different MAC addresses, and station(s) associated with the non-AP MLD may have different MAC addresses. Access points in the AP MLD having different MAC addresses may be in charge of each link and may act as independent access points (APs).

Stations in the non-AP MLD having different MAC addresses may be in charge of each link and may act as independent stations (STAs). Non-AP MLD may be referred to as STA MLD. The MLD may support a simultaneous transmit and receive (STR) operation. In this case, the MLD can perform a transmit operation on link 1 and a receive operation on link 2. MLD supporting STR operation may be referred to as STR MLD (eg, STR AP MLD, STR non-AP MLD). In embodiments, a link may mean a channel or a band. A device that does not support the STR operation may be referred to as NSTR (non-STR) AP MLD or NSTR non-AP MLD (or NSTR STA MLD).

MLD can transmit and receive frames in multiple links by using a non-contiguous bandwidth extension method (eg, 80 MHz + 80 MHz). Multi-link operation may include multi-band transmission. An AP MLD may include a plurality of access points, and the plurality of access points may operate on different links. Each of the plurality of access points may perform function(s) of a lower MAC layer. Each of the plurality of access points may be referred to as a "communication node" or a "sub-entity". A communication node (ie, an access point) may operate under the control of an upper layer (or the processor 110 shown in FIG. 1). A non-AP MLD may include a plurality of stations, and the plurality of stations may operate on different links. Each of the plurality of stations may be referred to as a "communication node" or a "sub-entity". A communication node (ie, a station) may operate under the control of an upper layer (or the processor 110 shown in FIG. 1).

MLD can perform communication in multi-band. For example, MLD may perform communication using a 40 MHz bandwidth according to a channel extension method (eg, bandwidth extension method) in a 2.4 GHz band, and communicate using a 160 MHz bandwidth according to a channel extension method in a 5 GHz band. can be performed. The MLD may perform communication using a 160 MHz bandwidth in a 5 GHz band and may perform communication using a 160 MHz bandwidth in a 6 GHz band. One frequency band (eg, one channel) used by the MLD may be defined as one link. Alternatively, a plurality of links may be established in one frequency band used by the MLD. For example, the MLD can establish one link in the 2.4 GHz band and two links in the 6 GHz band. Each link may be referred to as a first link, a second link, a third link, and the like. Alternatively, each link may be referred to as link 1, link 2, link 3, and the like. A link number may be set by an access point, and an ID (identifier) may be assigned to each link.

An MLD (eg, an AP MLD and/or a non-AP MLD) may establish multiple links by performing an access procedure and/or a negotiation procedure for multi-link operation. In this case, the number of links and/or links to be used among multiple links may be set. A non-AP MLD (eg, a station) may check information on a band capable of communicating with the AP MLD. In a negotiation procedure for multi-link operation between the non-AP MLD and the AP MLD, the non-AP MLD may configure one or more links among links supported by the AP MLD to be used for the multi-link operation. A station that does not support multi-link operation (eg, an IEEE 802.11a/b/g/n/ac/ax station) may be connected to one or more links among multiple links supported by the AP MLD.

When a band interval between multiple links (eg, a band interval between link 1 and link 2 in the frequency domain) is sufficient, the MLD may perform the STR operation. For example, the MLD may transmit PPDU (physical) layer protocol data unit (PPDU) 1 using link 1 of multiple links, and may receive PPDU 2 using link 2 of multiple links. On the other hand, if the MLD performs the STR operation when the band interval between multiple links is not sufficient, in-device coexistence (IDC) interference, which is interference between multiple links, may occur. Therefore, if the bandwidth interval between multiple links is not sufficient, the MLD may not be able to perform the STR operation. A link pair having the aforementioned interference relationship may be a Non Simultaneous Transmit and Receive (NSTR) limited link pair. Here, the MLD may be NSTR AP MLD or NSTR non-AP MLD.

For example, multiple links including link 1, link 2, and link 3 may be established between the AP MLD and the non-AP MLD 1. If the bandwidth interval between

links

1 and 3 is sufficient, the AP MLD may perform STR

operation using links

1 and 3. That is, the AP MLD can transmit frames using link 1 and receive frames using link 3. If the bandwidth interval between

links

1 and 2 is not sufficient, the AP MLD may not be able to perform STR

operation using links

1 and 2. If the bandwidth interval between

links

2 and 3 is not sufficient, the AP MLD may not be able to perform STR

operation using links

2 and 3.

Meanwhile, a negotiation procedure for multi-link operation may be performed in an access procedure between a station and an access point in a wireless LAN system.

A device (eg, access point, station) supporting multiple links may be referred to as a multi-link device (MLD). An access point supporting multiple links may be referred to as an AP MLD, and a station supporting multiple links may be referred to as a non-AP MLD or STA MLD. The AP MLD may have a physical address (eg MAC address) for each link. The AP MLD may be implemented as if an AP in charge of each link exists separately. A plurality of APs can be managed within one AP MLD. Accordingly, coordination between a plurality of APs belonging to the same AP MLD may be possible. The STA MLD may have a physical address (eg, MAC address) for each link. The STA MLD may be implemented as if an STA in charge of each link exists separately. A plurality of STAs may be managed within one STA MLD. Accordingly, coordination between a plurality of STAs belonging to the same STA MLD may be possible.

For example, each of AP1 of the AP MLD and STA1 of the STA MLD may be in charge of a first link and may perform communication using the first link. Each of AP2 of the AP MLD and STA2 of the STA MLD may be in charge of the second link and may communicate using the second link. STA2 may receive state change information for the first link from the second link. In this case, the STA MLD may collect information (eg, state change information) received from each link, and may control an operation performed by STA1 based on the collected information.

Next, methods for transmitting and receiving data in a wireless LAN system will be described. Even when a method (for example, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is described as a method performed in the first communication node and a method (eg, signal transmission or reception) For example, receiving or transmitting a signal) may be performed. That is, when the operation of the STA is described, the corresponding AP may perform an operation corresponding to the operation of the STA. Conversely, when the operation of the AP is described, the corresponding STA may perform an operation corresponding to the operation of the AP. In an embodiment, the operation of the STA may be interpreted as the operation of the STA MLD, the operation of the STA MLD may be interpreted as the operation of the STA, the operation of the AP may be interpreted as the operation of the AP MLD, and the operation of the AP MLD can be interpreted as an operation of the AP.

3 is a timing diagram illustrating a first embodiment of a slot allocation method of a slot-based restricted TWT (Restricted Target Wake Time).

Referring to FIG. 3 , the STA may transmit a TWT Setup Request frame to the AP to negotiate Restricted TWT (rTWT). The AP may receive a TWT setup request frame from the STA. The AP may generate a TWT setup response frame including parameters used by the STA and transmit the TWT setup response frame to the STA. The STA may receive a TWT setup response frame from the AP. rTWT may be established by exchanging the TWT setup request frame and the TWT setup response frame. The TWT setup request frame and the TWT setup response frame may be action frames. rTWT may be set according to a broadcast TWT setting procedure. When the broadcast TWT configuration procedure is performed, the rTWT ID may be allocated to the STA.

In addition, when the broadcast TWT setting procedure is performed, the STA includes Target Beacon Transmission Time (TBTT), which is the transmission time of a beacon frame including rTWT service period (SP) information (eg, wake TBTT) and rTWT SP information It is possible to know the transmission time interval (Interval between wake TBTTs) of the beacon frame. That is, the STA can know the transmission time of the beacon frame including the rTWT SP information by performing the broadcast TWT setup procedure. The AP may transmit beacon frames including rTWT SP information at regular intervals. That is, a beacon frame including rTWT SP information may be transmitted according to a specific period. A beacon frame including rTWT SP information may include SP information that is a section in which rTWT operates. The SP information may indicate time information (eg, start time, end time, and/or duration) of an SP located after the currently transmitted beacon frame. A beacon frame may include one or more SP information.

The STA can know the transmission time of the beacon frame including the rTWT SP information through the TBTT obtained through the broadcast TWT setting procedure, can receive the beacon frame from the AP at the transmission time, and rTWT SP included in the beacon frame information can be checked. The beacon frame may include start time information of SPs identified by rTWT IDs and duration information of SPs. The STA may obtain SP information of the rTWT to which the STA belongs based on the rTWT ID obtained through the previous broadcast TWT setup procedure.

In the broadcast TWT setup procedure, a time slot (TS) belonging to the SP may be allocated to the STA. The broadcast TWT setup procedure may include an exchange procedure of a TWT setup request frame and a TWT setup response frame. An STA may receive data from a TS allocated for it. That is, the STA may receive data up to the TS. The TS may operate with a target time at which data should be received. TS can be allocated based on two methods. As a first method, the TS offset subfield and the TS duration subfield of the TWT element included in the TWT setup request frame and/or the TWT setup response frame may be used to allocate TS. In the second method, the "nominal minimum TWT wake duration subfield" of the TWT element included in the TWT setup request frame and / or the TWT setup response frame can be interpreted as a TS offset and a TS duration, and the above interpretation Based on the TS can be allocated. The size of the “Nominally Minimum TWT Wake Duration Subfield” may be 8 bits.

The STA may receive a physical layer protocol data unit (PPDU) in a section including a TS allocated within the rTWT SP. PPDU transmission may be initiated before or after the start time of the TS allocated to the STA, but the PPDU transmitted from the TS may include a MAC layer protocol data unit (MPDU) of the STA to which the TS is allocated. Since a PPDU transmitted outside the TS allocated to the STA does not include the MPDU of the corresponding STA, the STA may not decode the PPDU outside the TS. In an embodiment, a PPDU may mean a data frame.

Referring to FIG. 4 , a frame may include a TWT element, and the TWT element may include element ID, length, control, and TWT parameter information. Each of the TWT setup request frame and the TWT setup response frame may have the frame format shown in FIG. 4 . Negotiation type 1 included in the control of the TWT element may be a type that negotiates a next wake TBTT time of the broadcast TWT and an interval between wake TBTTs. TWT information frame disabled set by the STA may indicate that reception of the TWT information frame is released by the STA. If the AP sets the TWT information frame disable to 1, this may indicate including time slot information for the slot-based restricted TWT. If the NDP paging indicator is set to 1 in the TWT setup request frame and the TWT setup response frame transmitted and received for TWT setup, this may indicate rTWT setup.

When the AP sets the NDP paging indicator to 1, 1 bit following the wake duration unit may be interpreted as a TS unit to indicate TS information of rTWT. The NDP paging indicator, wake duration unit, and TS duration unit indicated by the TS unit may be shown in Table 1 below.

When the NDP paging indicator of the TWT setup response frame transmitted by the AP is 0, the TS unit is meaningless because the TWT setup is a parameter setup for normal TWT. Accordingly, if the wake duration unit is 0, the TS duration unit may indicate 256us. If the wake duration unit is 1, the TS duration unit may indicate 1024 us, which is 1 TU (Transmission Unit).

An AP may allocate a TS to a STA based on two methods. As a first method, the TWT element included in the TWT setup request frame and / or the TWT setup response frame may include a TS offset subfield and a TS duration subfield, and the TS uses the TS offset subfield and the TS duration subfield. can be assigned. In the second method, the nominal minimum TWT wake duration subfield of the TWT element included in the TWT setup request frame and / or the TWT setup response frame may be interpreted as a TS offset and a TS duration, and based on the above interpretation, the TS is assigned It can be.

In the first method, the TS offset subfield may indicate an offset from the start of the SP (eg, rTWT SP) to the start of the TS, and the offset may be expressed in a unit indicated by the TS duration unit. . The TS duration subfield may indicate the duration from the start of the TS, and the duration may be expressed in a unit indicated by a TS duration unit. For example, "when the TS duration unit is 128us, the TS offset is 4, and the TS duration is 2", the start time of the TS may be a time point after 4×128us from the start time of the SP, and the duration of the TS is It can be 2×128 us.

In the second method, the first x bits of the nominally minimum TWT wake duration subfield can be interpreted as a TS duration, and the remaining y bits of the nominally minimum TWT wake duration subfield can be interpreted as a TS offset. x can be 5 and y can be 3. When the second method is used, in order to indicate the TS offset, the length of the TS allocated to STAs belonging to the rTWT SP may be the same length indicated by the TS duration. Alternatively, a TS duration that is an integer multiple of the shortest TS duration among TSs allocated to STAs belonging to the rTWT SP may be used. For example, "the TS duration unit is 128us, the TS duration assigned to STA1 is 1, the TS offset assigned to STA1 is 0, the TS duration assigned to STA2 is 1, and the TS offset assigned to STA2 is 2. , the TS duration allocated to STA3 is 1, and the TS offset allocated to STA3 is 1", a TS with a length of 128us from the start of the SP (ie, the time when the TS offset is 0) can be allocated to STA1, , A 128us long TS from the start of the SP to the TS offset (i.e., 1×128us) can be allocated to STA3, and a 128us long TS from the start of the SP to the TS offset (i.e., 2×128us) TS may be assigned to STA2.

Referring to FIG. 5, resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 16TU (16384 us). A TS duration of 4TU (4096us) may be set for each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 4TU, the TS offset of STA3 may be 8TU, and the TS offset of STA4 may be 12TU. Accordingly, from the start of the rTWT SP, 4TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

Each STA may obtain data by performing a decoding operation on the PPDU in the TS allocated to the STA. The AP may perform a channel sensing procedure and a backoff procedure, which are channel access procedures, in order to transmit a data frame. If the channel access procedure succeeds, since the first TS is a transmission interval allocated to STA1, the AP can transmit a data frame for STA1 in the first TS. A transmit opportunity (TXOP) duration set as the channel access procedure succeeds may fall within the TXOP limit and may include the first TS. The TXOP limit value may be different for each TXOP limit AC. The maximum TXOP limit may be 4TU (4096us). Since the TS duration allocated to each STA is 4TU, as the channel access procedure succeeds, the configurable TXOP duration may be set to a value within the maximum TXOP limit (eg, 4TU). STA1 can receive a PPDU from the TS allocated to it and obtain data by performing a decoding operation on the PPDU.

After transmitting the first data frame to STA1 in the first TS, the AP may perform a channel access procedure to transmit the second data frame to STA2. If the channel access procedure succeeds, the AP may transmit a second data frame to STA2. The second data frame may be transmitted in the second TS in the rTWT SP. STA2 can receive the PPDU from the TS allocated to it and obtain data by performing a decoding operation on the PPDU.

After transmitting the second data frame to STA2 in the second TS, the AP may perform a channel access procedure to transmit the third data frame to STA3. If the channel access procedure succeeds, the AP may transmit a third data frame to STA3. The channel access procedure may be completed before the start time of the TS allocated to STA3. In this case, PPDU transmission for STA3 may be initiated before the TS start time. Since the transmission period of the data frame (eg, PPDU) includes the TS allocated to STA3, STA3 can obtain data by performing a decoding operation on the PPDU received from the AP.

After transmitting the third data frame to STA3 in the third TS, the AP may perform a channel access procedure to transmit the fourth data frame to STA4. If the channel access procedure succeeds, the AP may transmit the fourth data frame to STA4. The channel access procedure may be completed before the start time of the TS allocated to STA4. In this case, PPDU transmission for STA4 may be initiated before the TS start time. In addition, PPDU transmission for STA4 may be completed before the start of TS. That is, the transmission interval of the data frame (eg, PPDU) may not include the TS allocated to STA4. In this case, the AP may add padding to the data frame so that the transmission period of the data frame includes the TS allocated to STA4. Since the transmission period of “data frame + padding” includes the TS allocated to STA4, STA4 can obtain data by performing a decoding operation on the PPDU received from the AP. Alternatively, if "transmission of the fourth data frame ends before the TS allocated to STA4 or the remaining duration exists in rTWT SP1", STA4 may perform uplink channel transmission in the TS allocated to STA4. Alternatively, STA1, STA2, STA3, and STA4 participating in the rTWT SP in the TS allocated to STA4 may transmit uplink frames through a channel access procedure. Alternatively, the AP may terminate the rTWT SP early.

Referring to FIG. 6, resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 8TU (8192us). The TS duration of 2TU (2048us) may be set for each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 2TU, the TS offset of STA3 may be 4TU, and the TS offset of STA4 may be 6TU. Accordingly, from the start of the rTWT SP, 2TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

Each STA may obtain data by performing a decoding operation on the PPDU in the TS allocated to the STA. The AP may perform a channel sensing procedure and a backoff procedure, which are channel access procedures, in order to transmit a data frame. The transmission procedure for STA1 and STA2 in FIG. 6 may be the same as the transmission procedure for STA1 and STA2 in FIG. 5 described above.

The AP may perform a channel access procedure to transmit the third data frame. The channel access procedure may succeed before the start of the third TS. When the following condition(s) are satisfied, the AP may combine data frames for STA3 and STA4 in an A (aggregated)-MPDU form and transmit the A-MPDU form data frame.

-Condition 1: "STA3 data frame + delimiter + STA4 data frame" ≤ TXOP limit

- Condition 2: When "STA3 data frame + separator + STA4 data frame" can be transmitted in TS of STA3 and TS of STA4

In the above-described embodiment, the A-MPDU may be composed of "MPDU of STA3 + delimiter + MPDU of STA4 + delimiter + TF (Trigger Frame)". TF may allocate resources for transmission of BA (block ACK) frames for MPDUs received in STA3 and STA4. The BA frame may be a reception response frame. Since the transmission interval (eg, TXOP duration or PPDU length) of the A-MPDU includes the TS allocated to STA3 and STA4, each of STA3 and STA4 can receive the A-MPDU, and decoding operation for the A-MPDU can be performed. When the RA (Receiver Address) included in the MAC header of the first MPDU included in the A-MPDU indicates STA3, STA3 may obtain the first MPDU. When the RA included in the MAC header of the second MPDU included in the A-MPDU indicates STA4, STA4 may obtain the second MPDU. Since the RA included in the TF is set as a broadcast address, STA3 and STA4 can obtain channel allocation information for BA transmission by performing a decoding operation on the TF.

When the PPDU in the A-MPDU format is received, the STA4 may check the TXOP duration or the PPDU length based on the preamble of the PPDU. When the RA included in the MAC header of the first MPDU included in the PPDU in the form of A-MPDU is its own address, a multicast address including itself, or a broadcast address including itself, the STA included in the PPDU A decoding operation may be performed on the first MPDU. On the other hand, if the RA included in the MAC header of the first MPDU included in the A-MPDU type PPDU does not indicate its address, the STA does not transmit during the TXOP period indicated by the A-MPDU. Can set NAV there is. However, in the operation according to the slot-based rTWT, regardless of the receiver of the first MPDU included in the A-MPDU transmitted in the interval including the TS allocated to the STA, the STA decodes the A-MPDU without NAV setting can be performed.

Alternatively, "when the above conditions (eg, condition 1, condition 2) are satisfied" or "a DL multi-user (MU) PPDU to STA3 and STA4 (eg, HE MU PPDU, EHT MU PPDU) is less than the TXOP limit or less than the sum of the TSs of STA3 and STA4", the AP may configure and transmit data frames to be received by STA3 and STA4 in the form of a DL MU PPDU. The DL MU PPDU may be transmitted in an orthogonal frequency division multiple access (OFDMA) scheme. The DL MU PPDU configured by the AP may include MPDUs transmitted to STA3 and STA4, and may include TF for resource allocation for the BA frame. Upon receiving the DL MU PPDU of the AP, STA3 and STA4 may decode the MPDU(s) included in the DL MU PPDU and may transmit BA frames to the AP according to uplink resource allocation allocated by the TF.

7A is a timing diagram illustrating a third embodiment of a communication method according to a slot-based limited TWT, FIG. 7B is a timing diagram illustrating a fourth embodiment of a communication method according to a slot-based limited TWT, and FIG. 7C is a timing diagram illustrating a fifth embodiment of a communication method according to slot-based limited TWT.

Referring to FIGS. 7A to 7C , resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 4TU (4096 us). A TS duration of 1TU (1024us) may be set for each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 1TU, the TS offset of STA3 may be 2TU, and the TS offset of STA4 may be 3TU. Accordingly, from the start of the rTWT SP, 1TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

The AP may perform a channel sensing procedure and a backoff procedure, which are channel access procedures, in order to transmit a data frame. If the channel access procedure is successful, the AP may set the TXOP duration to the maximum TXOP limit (eg, 4TU) and transmit the first data frame to STA1. The AP may receive the BA frame after a short interframe space (SIFS) from the transmission time of the first data frame. In this case, TXOP can be successfully configured, and the AP can transmit data frames at SIFS intervals within TXOP. That is, continuous transmission may be possible in a “data frame + SIFS + BA frame + data frame + SIFS + BA frame” method within the TXOP. Access categories (AC) of data frames transmitted in TXOP may be the same or different. Also, the recipients of the data frames transmitted within the TXOP may be the same or different. If the BA frame is not received after SIFS from the transmission time of the first data frame, TXOP configuration may fail. In this case, the AP may perform a backoff procedure (eg, channel access procedure) again to transmit the second data frame.

In the embodiment of FIG. 7A, since the TXOP duration is 4TU, the corresponding TXOP may include TSs of all of STA1, STA2, STA3, and STA4. A data frame transmission procedure may be initiated after the start of the TS. If the length of the previous data frame is short, the transmission procedure of the next data frame may be initiated prior to the start of the TS. In this case, the AP may add padding to the previous data frame so that the transmission procedure of the next data frame is started after the start of the TS. For example, when the length of the first data frame is short, the AP may transmit the first data frame to which padding is added. A time after SIFS from the BA frame reception time for the first data frame may be the start time of TS of STA2. Accordingly, the AP may transmit the second data frame to STA2. The length of the third data frame (ie, the data frame of STA3) may be long, and in this case, the BA frame for the third data frame may be received after the TS of STA3. Alternatively, even when the BA frame for the third data frame is received in the TS of STA3, the transmission procedure of the fourth data frame (ie, the data frame of STA4) may be initiated after the start time of the TS of STA4. Even in the case described above, there is no problem if the transmission procedure of the fourth data frame is initiated within the TS of STA4.

In the embodiment of FIG. 7B , padding may be added to the BA frame for the data frame in order to initiate the transmission procedure of the data frame at the start of the TS. To support this operation, the AP may generate a header (eg, MAC header) including information indicating adding padding to the BA frame (hereinafter referred to as "padding indicator"), and the corresponding header It is possible to transmit a data frame including. The padding indicator may be indicated through the SRS control subfield of A-control. The SRS control subfield may indicate the PPDU response duration. The PPDU response duration may indicate the duration of a BA frame that is a response to the PPDU. The STA may add padding to the BA frame so that the duration of the BA frame corresponds to the PPDU response duration.

In the embodiment of FIG. 7C , when the BA frame is successfully received after SIFS from the transmission time of the first data frame, TXOP may be set. That is, when the exchange of the first data frame is successfully completed, TXOP may be set. In the slot-based rTWT operation, a point coordination function (PCF) interframe space (PIFS) recovery procedure may be performed without successful exchange of the first data frame. If the BA frame is not received in the PIFS from the transmission time of the first data frame, the AP may retransmit the first data frame. If the retransmission period of the first data frame invades the second TS (ie, the TS of STA2), the AP may not retransmit the first data frame. If the first data frame is not retransmitted, frame transmission may not be performed until the start of the second TS. In this case, other communication nodes may steal the transmission opportunity. Accordingly, the AP may transmit the QoS Null frame until the start of the second TS, and may transmit the second data frame to the STA2 at the start of the second TS.

Alternatively, if the following conditions apply, the AP may transmit the second data frame to the STA2 after the PIFS from the transmission time of the first data frame. In addition, the AP may add padding to the second data frame in consideration of the transmission time of the third data frame. Alternatively, the AP may instruct STA2 to add padding to the BA frame for the second data frame.

- Condition: "If the transmission procedure of the second data frame is initiated before the start of the second TS, and the transmission period of the second data frame includes the second TS", STA2 can receive the second data frame .

Referring to FIG. 8 , resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 4TU (4096 us). A TS duration of 1TU (1024us) may be set for each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 1TU, the TS offset of STA3 may be 2TU, and the TS offset of STA4 may be 3TU. Accordingly, from the start of the rTWT SP, 1TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

The AP may perform a channel sensing procedure and a backoff procedure, which are channel access procedures, in order to transmit a data frame. If the channel access procedure is successful, the AP may set the TXOP duration to the maximum TXOP limit (eg, 4TU) and transmit the first data frame to STA1. 4TU may be enough time to include TSs of all STAs assigned to the rTWT SP. In this case, the AP may generate a PPDU in the form of an A-MPDU including MPDUs of all STAs and transmit the PPDU. In order to distinguish the MPDU of each STA within the PPDU, a delimiter may be inserted between the MPDUs. When the TXOP duration of the A-MPDU includes its TS, the STA may perform a decoding operation on all MPDUs included in the A-MPDU. An STA may acquire an MPDU indicated as a receiver among MPDUs. If the transmission period of the A-MPDU does not include TSs of all STAs, the AP may add padding to the corresponding A-MPDU so that the transmission period of the A-MPDU includes TSs of all STAs.

In order for all STAs to receive the A-MPDU, each RA of all MPDUs included in the A-MPDU may be set to a multicast address or group address indicating all STAs assigned to rTWT SP1. In this case, all STAs assigned to rTWT SP1 may perform a decoding operation on the A-MPDU regardless of whether the transmission period of the A-MPDU includes a TS. The STA may know the allocation order of STAs in rTWT SP1. Accordingly, the STA may obtain its own MPDU from among MPDUs included in the A-MPDU according to the STA's allocation order.

The RA of the MAC header of the MPDU may be set to a multicast address or a group address, and the above-described A-MPDU may be included in the payload of the corresponding MPDU. When the RA of the data frame is set to a multicast address indicating all STAs allocated in rTWT SP1, all STAs can receive the data frame, and decoding of the A-MPDU included in the payload of the data frame By additionally performing, it is possible to obtain its own MPDU.

Alternatively, the AP may configure and transmit data frames to be received by STA1, STA2, STA3, and STA4 in the form of downlink multi-user (DL MU) PPDUs (eg, HE MU PPDU, EHT MU PPDU). The DL MU PPDU may be transmitted in an orthogonal frequency division multiple access (OFDMA) scheme. The DL MU PPDU configured by the AP may include MPDUs transmitted to STA3 and STA4, and may include TF for resource allocation for the BA frame. STA1, STA2, STA3, and STA4 receiving the DL MU PPDU from the AP can decode the MPDU(s) included in the DL MU PPDU, and transmit BA frames to the AP according to the uplink resource allocation allocated by the TF. there is.

9A is a timing diagram illustrating a communication method according to a slot-based limited TWT according to a seventh embodiment, and FIG. 9B is a timing diagram illustrating a communication method according to a slot-based limited TWT according to an eighth embodiment.

Referring to FIGS. 9A and 9B , resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 16TU (16384 us). A TS duration of 2TU (2048us) may be set for downlink transmission of each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 2TU, the TS offset of STA3 may be 4TU, and the TS offset of STA4 may be 6TU. Accordingly, from the start of the rTWT SP, 2TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. That is, the total TS duration for all downlink transmissions of STA1, STA2, STA3, and STA4 may be 8TU. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

Operations for downlink of STA1 to STA4 may be performed the same as or similar to the embodiments shown in FIGS. 5 to 8 . Of the total 16TUs of rTWT SP1, the remaining 8TUs may be allocated for uplink transmission of STA1 to STA4.

Referring to FIG. 9A, 8TUs not allocated to STA(s) in rTWT SP1 may be referred to as 'UL intervals'. In the UL period, the AP may transmit TFs for uplink resource allocation of STA1 to STA4. STA1 to STA4 may decode the TF of the AP and check resource allocation information (eg, sub-channel information, uplink resource time information) indicated by the AP. STA1 to STA4 may transmit an uplink PPDU after SIFS from the time of reception of the TF by OFDMA method using resource allocation information indicated by the TF. The AP may receive UL PPDUs (eg, UL data) of STA1 to STA4, and may transmit a multi-STA BA as a response to the UL data.

Referring to FIG. 9B, 8TUs not allocated to STA(s) in rTWT SP1 may be referred to as 'UL intervals'. In the UL interval, STA1 to STA4 may transmit uplink data through channel contention. For example, STA1, STA3, and STA4 may transmit uplink data through channel contention and may receive a BA frame as a response to the uplink data from the AP. If uplink data to be transmitted does not exist in STA2, STA2 may not transmit in the UL interval.

Referring to FIG. 10, resources for STA1, STA2, STA3, and STA4 may be allocated within rTWT SP1. The duration of rTWT SP1 may be 16TU (16384 us). A TS duration of 4TU (4096us) may be set for downlink transmission of each of STA1, STA2, STA3, and STA4. The TS offset of STA1 may be 0, the TS offset of STA2 may be 4TU, the TS offset of STA3 may be 8TU, and the TS offset of STA4 may be 12TU. Accordingly, from the start of the rTWT SP, 4TU-length TSs may be sequentially allocated to STA1, STA2, STA3, and STA4. Each of the TSs of STA1, STA2, STA3, and STA4 may be set by the exchange procedure of the TWT setup request frame and the TWT setup response frame shown in FIG. 3 .

In the assigned TS, STA1 to STA4 can receive downlink data of the AP and transmit uplink data. For example, AP1 may transmit downlink data to STA1 in the first TS allocated for STA1. The AP may indicate available time resources for uplink by STA1 using a reverse direction grant (RDG), and STA1 may transmit uplink data to AP1 using a reverse direction (RD) method based on information indicated by the RDG. can transmit Alternatively, STA1 may transmit uplink data to the AP within the TS allocated to STA1 by performing a separate channel access procedure after downlink transmission of the AP is completed. STA2 to STA4 may also perform a downlink data reception operation and an uplink data transmission operation in the same or similar manner to that of STA1 described above.

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims below. You will be able to.

Claims

As a method of an access point (AP),

Setting a first time slot (TS) for a first station (STA);

Setting a second TS for a second STA;

Transmitting the first data frame of the first STA in the first TS; and

Transmitting a second data frame of the second STA in a transmission period including the second TS,

The first TS and the second TS are sequentially set within a restricted target wake time (rTWT) service period (SP).
The method of claim 1,

Setting the first TS for the first STA includes:

Receiving a TWT setup request frame from the first STA; and

Transmitting a TWT setup response frame to the first STA in response to the TWT setup request frame;

At least one of the TWT setup request frame and the TWT setup response frame includes offset information and duration information of the first TS, and the offset information is from the start time of the rTWT SP to the start time of the first TS A method of an AP indicating an offset to.
The method of claim 2,

Among the nominal minimum TWT wake duration included in the TWT setup request frame or the TWT setup response frame, x bits indicate the offset information, and among the nominal minimum TWT wake duration, y bits indicate the duration information, wherein each of x and y is a natural number.
The method of claim 1,

Each of the first data frame and the second data frame is transmitted after a successful channel access procedure.
The method of claim 1,

The transmission procedure of the second data frame is initiated after "the first data frame + short interframe space (SIFS) + reception response frame + SIFS".
The method of claim 1,

Padding is added to the first data frame so that the transmission procedure of the second data frame is started after the start of the second TS.
The method of claim 1,

The method of the AP, wherein the header of the first data frame includes information indicating adding padding to a reception response frame for the first data frame.
As a method of STA (station),

Transmitting a TWT setup request frame to an access point (AP);

Receiving a TWT setup response frame from the AP in response to the TWT setup request frame; and

Receiving a data frame from the AP within a time slot (TS) established by exchanging the TWT setup request frame and the TWT setup response frame,

The method of the STA, wherein the TS is set within a restricted target wake time (rTWT) service period (SP).
The method of claim 8,

At least one of the TWT setup request frame and the TWT setup response frame includes offset information and duration information of the TS, and the offset information includes an offset from the start time of the rTWT SP to the start time of the TS Instructing, the method of the STA.
The method of claim 9,

Among the nominal minimum TWT wake duration included in the TWT setup request frame or the TWT setup response frame, x bits indicate the offset information, and among the nominal minimum TWT wake duration, y bits indicate the duration information, The method of the STA, wherein each of x and y is a natural number.
The method of claim 8,

The method of the STA,

Transmitting a reception response frame for the data frame to the AP,

When the header of the data frame includes information indicating that padding is added to the reception response frame for the data frame, the padding is added to the reception response frame.
As an access point (AP),

processor; and

a memory storing one or more instructions executed by the processor;

The one or more commands,

setting a first time slot (TS) for a first station (STA);

configure a second TS for a second STA;

Transmit the first data frame of the first STA in the first TS; and

Executed to transmit a second data frame of the second STA in a transmission period including the second TS,

The first TS and the second TS are sequentially set within a restricted target wake time (rTWT) service period (SP).
The method of claim 12,

When configuring the first TS for the first STA, the one or more commands,

Receiving a TWT setup request frame from the first STA; and

Further executed to transmit a TWT setup response frame to the first STA in response to the TWT setup request frame;

At least one of the TWT setup request frame and the TWT setup response frame includes offset information and duration information of the first TS, and the offset information is from the start time of the rTWT SP to the start time of the first TS Pointing to an offset to, AP.
The method of claim 13,

Among the nominal minimum TWT wake duration included in the TWT setup request frame or the TWT setup response frame, x bits indicate the offset information, and among the nominal minimum TWT wake duration, y bits indicate the duration information, Each of x and y is a natural number, AP.
The method of claim 12,

Wherein each of the first data frame and the second data frame is transmitted after a channel access procedure succeeds.
The method of claim 12,

The transmission procedure of the second data frame is initiated after "the first data frame + short interframe space (SIFS) + reception response frame + SIFS".
The method of claim 12,

Padding is added to the first data frame so that a transmission procedure of the second data frame is started after the start of the second TS.
The method of claim 12,

The header of the first data frame includes information indicating adding padding to a reception response frame for the first data frame.